The best way to move multiple notebooks at the same time from one folder to another is by using the Databricks workspace API to export and then import the notebooks into the new folder. This can be done from the UI at the top of the screen near to the Share option, on the 3 vertical dots you can select export option, this will generate a file with all the notebooks and folders on the page, then you can import them in the desired folder.

To do it programmatically you can refer to KB: https://kb.databricks.com/notebooks-internal/1333098-how-to-migrate-shared-folders-and-the-notebooks